Effect of Gamma Irradiation on Different Enzymatic Activities in Spongy Tissue Development of Mango Fruit 'Ataulfo', Poster Board #039

The hot water treatment (46.1 °C for 75–110 min.) is a mandatory process to export mango fruit from Mexico to the United States and others countries in order  to prevent the spread of Mexican fruit fly (Anastrepha ludens), but this process affects the fruit sensory quality. Radiation with gamma rays into 0.15 to 1.0 kGy range is a safety alternative to this treatment which is approved by FDA and APHIS offices. Previous data indicated that mango cv ‘Ataulfo’ irradiated at doses ≥ 0.84 kGy developed spongy tissue and internal color changes but its origin is unknown. The aim of this work was to determine changes in the microstructure, weight loss (WL), total soluble solids (TSS), total starch (TS), total sugars (TSU), and α and β activity-amylase, phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) in mango cv. ‘Ataulfo’ from Oaxaca, Mexico, in maturity ¾ stage irradiated at 0, 0.6, and 1.0 kGy, stored for 19 days at 10 °C, 20 °C, and transferred from 10 °C to 20 °C. Spongy tissue development was observed at ≥ 0.6 kGy dose, indicating higher susceptibility respect of previous reports. At 10 °C, the variables values were statistically lower than 20 °C except α and β activity-amylases. At 1 kGy and 10 °C, the TSS and TSU values were lower (9.2 °Brix and 8.43 mg/100 g) in fruits with spongy tissue respect to control fruit (13.2 °Brix and 22.08 mg/100 g, respectively); the β-amylase activity was higher for the same temperature and irradiation dose (12.53 mg maltose/mg protein min) than control fruits (10.57 mg maltose/mg protein min). TS content gradually decreased (10% to 1.6%) while TSU increased over the time. Fruits at 20 °C and 1.0 kGy, showed maximum α and β-amylase activities and spongy tissue development in comparison to control fruit (36.89 and 20.60 mg maltose/mg protein min, respectively). The activities of PPO and PAL did not explain the color changes. The behavior of amylases activities did not explain completely the spongy tissue development and although there were micro structural changes in the tissue there was not a clear relationship with the dose applied.